Reproductive biology of two marine catfishes (Siluriformes, Ariidae) in the Sepetiba Bay, Brazil

Marine catfish are abundant in the Sepetiba Bay, a 305 km2 area in Southeast Brazilian coast (Lat. 22 degrees 54' - 23 degrees 04' S: Long. 43 degrees 44' - 44 degrees 10' W), but the knowledge on their biology is still scanty. The reproductive biology of Sciadeichthys luniscutis (Valenciennes 1840) and Genidens genidens (Valenciennes 1839) was studied through monthly sampling, from October 1998 to September 1999. Fishes were caught with a standardized otter trawl, in the interior of Sepetiba Bay, and near to the confluence with a major freshwater contributor. Six gonadal stages were described, based on macroscopic observations of gonad form, size, weight, color and oocyte diameter, and microscopic observations of differences in size and staining in the nucleus and cytoplasm structures, as viewed through a light microscope. Changes in the gonadosomatic index (GSI) and in stages of gonadal development showed what S. luniscutis spawned in Spring, while G. genidens spawned in Summer. Total spawning was shown for both species as indicated by high concentration of post-ovulatory follicles in spent stages. Fecundity was low (14-38 vitellogenic oocytes for S. luniscutis and 6-24 for G. genidens). when compared with other teleosts. Low fecundity and separation in spawning period suggest that both species are k-strategist, able to avoid interspecific competition in early stages of life cycle to optimize the use of the available niche.     

Sound production to electric discharge: sonic muscle evolution in progress in Synodontis spp. catfishes (Mochokidae)

Elucidating the origins of complex biological structures has been one of the major challenges of evolutionary studies. Within vertebrates, the capacity to produce regular coordinated electric organ discharges (EODs) has evolved independently in different fish lineages. Intermediate stages, however, are not known. We show that, within a single catfish genus, some species are able to produce sounds, electric discharges or both signals (though not simultaneously). We highlight that both acoustic and electric communication result from actions of the same muscle. In parallel to their abilities, the studied species show different degrees of myofibril development in the sonic and electric muscle. The lowest myofibril density was observed in Synodontis nigriventris, which produced EODs but no swim bladder sounds, whereas the greatest myofibril density was observed in Synodontis grandiops, the species that produced the longest sound trains but did not emit EODs. Additionally, S. grandiops exhibited the lowest auditory thresholds. Swim bladder sounds were similar among species, while EODs were distinctive at the species level. We hypothesize that communication with conspecifics favoured the development of species-specific EOD signals and suggest an evolutionary explanation for the transition from a fast sonic muscle to electrocytes.     

Linking micromorphism,brooding, and hermaphroditism in brachiopods: Insights from Caribbean Argyrotheca (Brachiopoda)

In extant brachiopods, parental brooding of the larvae occurs exclusively within Rhynchonelliformea. Methods of larval protection range from simple retention of the larvae within the mantle cavity, to sophisticated brood care within highly specialized brood pouches found in Argyrotheca and Joania (Terebratulida, Megathyridoidea), Gwynia (Terebratulida, Gwynioidea), and all Thecideoidea (Thecideida). Previous studies on the reproductive biology of Argyrotheca yielded contrasting results on the epithelial origin of the brood pouches in this genus. Here, representatives of different species of Argyrotheca from the Belize Barrier Reef were examined using histological section series. Brood pouches of four species, A. cf. schrammi and Argyrotheca sp. 1–3, are of the same basic structure, formed by invaginations of the anterior body wall and connected to the visceral cavity via the metanephridia. The same four species are simultaneously hermaphroditic, suggesting that fertilization is achieved, at least partly, through selfing. One species, Argyrotheca rubrocostata, differs significantly from all others as it has no brood pouch and gonochoric gonads. Thus, the presence of brood pouches and simultaneous hermaphroditism are concluded to be correlated within Megathyridoidea and proposed to be homologous traits of Joania and several but not all species of Argyrotheca, questioning the monophyletic status of both genera. In contrast to the brood pouches of Thecideoidea, lophophoral epithelium is not involved in the formation of the pouches of Argyrotheca and Joania. Therefore, megathyridoid and thecideoid brood pouches are not homologous but evolved independently within rhynchonelliform brachiopods. All brachiopods with brood pouches share a micromorphic form and a short life span, limiting the space and time available for gamete and larval development. We suggest that the brood pouches and the hermaphroditic gonads of Argyrotheca spp. and Joania compensate these limitations by minimizing the loss of gametes and larvae, and by maximizing the chances of successful fertilization. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

Gametogenesis and Development of Gymnocharacinus Bergi (Pisces, Characidae): Reproductive Mode Relative to Environmental Stability

Gymnocharacinus bergi (Pisces, Characidae) is classified as 'endangered' (IUCN 1996). It has been given particular attention among Patagonian fishes due to the reduction of some of its morphological structures, particularly scales, its extreme southern distribution among the Characiformes and its strong adaptation to a thermal environment in northeastern Patagonia. This paper describes the main aspects of gametogenesis, induced breeding, spawning and development of G. bergi, whose life history traits are related to the peculiar characteristics of its restricted environment. The temperature and flow stability of the Valcheta Stream make many of the environmental variables predictable. Other variables related to photoperiod undergo predictable fluctuation during the year. Gymnocharacinus bergi has synchronous gametogenesis and a rather short breeding season, which is earlier than for Paranensean characids. Its reproductive mode, courtship and spawning behaviour, and the absence of sexual dimorphism are common to other small characins from lotic environments. Gymnocharacinus bergi is a sedentary species with precocial characters, such as low fecundity and slightly adhesive, yolk-rich oocytes which are large in relation to the small size of the female. Larvae are robust, development is indirect and adulthood prolonged. These peculiar characteristics indicate a reproductive style very different from that of the main groups of Patagonian fish fauna.     

On the osteology and myology of catfish pectoral girdle, with a reflection on catfish (Teleostei: Siluriformes) plesiomorphies

The configuration of the pectoral girdle bones and muscles of numerous catfishes was studied in detail and compared with that of other siluriforms, as well as of other teleosts, described in the literature. The pectoral girdle of catfishes is composed of only three bones, which probably correspond to the posttemporo-supracleithrum (posttemporal + supracleithrum), scapulo-coracoid (scapula + coracoid), and cleithrum of other teleosts. These latter two bones constitute the place of origin of the pectoral girdle muscles. Two of these muscles are related to the movements of the pectoral fin. These two muscles correspond, very likely, to the abductor superficialis and to the adductor superficialis of other teleostean fishes. In relation to the pectoral spine (thickened first pectoral fin ray), it is usually moved by three well-developed muscles, which are probably homologous with the arrector ventralis, arrector dorsalis, and abductor profundus of nonsiluriform teleosts. The morphological diversity and the plesiomorphic configuration of these muscles, as well as of the other catfish pectoral girdle structures, are discussed.     

A phylogenetic analysis of the major groups of catfishes (Teleostei: Siluriformes) using rag1 and rag2 nuclear gene sequences

Higher-level relationships among catfishes were investigated by parsimony, maximum likelihood and Bayesian analyses of two nuclear genes across 110 catfish species representing 36 of 37 families and Conorhynchos (family incertae sedis). Analysis of 3660 aligned base pairs from the rag1 and rag2 genes confirms monophyly of Siluriformes, of most siluriform families and of a number of multifamily groups, some recognized, some novel. South American Loricarioidei are recovered as the sistergroup to other catfishes which are divided into Diplomystidae and Siluroidei. This result contrasts with the prevailing hypothesis that Diplomystidae is the sister to all other catfishes. Monophyly of Siluroidei is supported by rag data including a unique three-codon deletion from rag1. Deep within Siluroidei are 12 large, strongly supported groups with poorly resolved interrelationships. Five are single families: Cetopsidae, Plotosidae, Chacidae, Siluridae and Pangasiidae. Four others are monophyletic taxa ranked here as superfamilies: Clarioidea (Clariidae, Heteropneustidae), Arioidea (Ariidae, Anchariidae), Pimelodoidea (Pimelodidae, Pseudopimelodidae, Heptapteridae, Conorhynchos), Ictaluroidea (Ictaluridae, Cranoglanididae). South American Doradoidea (Doradidae, Auchenipteridae) and Aspredinidae are a sistergroup pair. Sisoroidea (without Aspredinidae), Ailia+Laides, Horabagridae, and Bagridae (without Rita) form a large, predominantly Asian clade, "Big Asia." Mochokidae, Malapteruridae, Amphiliidae, Claroteidae, and African schilbids are united as a species-rich African clade, "Big Africa." The three large continental clades, "Big Asia," "Big Africa" and Neotropical Loricarioidei suggest a prevalence of intracontinental diversification of catfishes. South America is the home of the Gymnotiformes, putative sistergroup of catfishes, plus two of the deepest siluriform clades, Loricarioidei and Diplomystidae, thus suggesting an ancient siluriform presence if not origin there. The rag phylogeny does not identify any African-South American catfish clade. The well-known African-Asian relationships within families Clariidae and Bagridae are confirmed, as is the recently found North American-Asian relationship between Ictaluridae and Cranoglanididae.     

Ultrastructure of the ampullary organs of Plicofollis argyropleuron (Siluriformes: Ariidae)

The morphology of ampullary organs in Plicofollis argyropleuron, collected from a southeast Queensland estuary, was examined by light and electron microscopy to assess the morphological characteristics of teleost ampullary organs in environments with fluctuating salinities. This catfish possesses both macroampullae and microampullae. Both have the typical teleost arrangement of an ampullary pore linked by a canal to a single ampulla that is lined with receptor and supportive cells. The canal wall of macroampullae consists of a collagen sheath, a basement membrane, and two layers of squamous epithelial cells adjacent to the lumen, joined by desmosomes and tight junctions near the surface of the epithelium. Ampullary pore diameters are similar in range for both the macroampullae and the microampullae, with microampullae always arising from the larger pores within a single region of the head. Canal length of the macroampullae is longer than those of the microampullae. Macroampullae also contain approximately 10 times as many receptor cells compared with the microampullae. In both organs, these pear‐shaped receptor cells alternate with supportive cells along the entire luminal surface of the ampulla. The apical region of receptor cells extends into the lumen and bears numerous microvilli. The basal region of receptor cells adjoins to either individual or multiple unmyelinated neural terminals. The coexistence of two markedly different ampullary organ morphologies within a single species support theories concerning the possible multifunctionality of these sensory organs. J. Morphol., 276:1405–1411, 2015. © 2015 Wiley Periodicals, Inc.     

Influences of the reproductive cycle on condition of marine catfishes (Siluriformes,Ariidae) in a coastal area at southeastern Brazil

Marine catfishes use estuaries and bays as part of their life cycle for spawning and feeding purposes, respectively. We compared three species of the family Ariidae in two different environmental conditionsa relatively stable bay site and an estuarine site, which differ in their magnitudes of environmental fluctuation to investigate effects of spawning on condition. We found differences in the parameter b (slope) and in they-intercept (a) among species and sexes. The parameter a varied inversely with b, and thus is not a good indicator to express fish condition. Condition factor did not differ between the two sites for species and sexes when we consider the pooled data. Overall condition was associated with reproductive process, and was high before the reproductive season, decreasing during the spawning period in the estuary, then increasing when fish move to the bay (April–August). Temporal segregation in the reproductive period and small-scale movements between the estuary and the bay are the probable mechanisms to optimize the use of the area by the three species.     

Early development and allometric shifts during the ontogeny of a marine catfish (Cathorops spixii‐Ariidae)

This study assessed whether the developmental series of the ariid Cathorops spixii (Agassiz, 1829) is related to growth patterns during its early ontogeny. The main morphological events of C. spixii were studied from the newly neurula embryo (6.99±0.69 mm TL) to juveniles (53.38±14.43 mm TL) in order to characterize and corroborate patterns of ontogenetic allometries. Prior to hatching, embryos were well‐developed, with an ossified axial and appendicular skeleton. Embryos grew slowly, but positive allometric growth was observed in head width (β₁ = 1.65) and eye diameter (β₁ = 1.59). This seems to be related to the fast development of sensory organs such as otoliths, Weberian apparatus, lenses, nostrils and barbels during the embryonic period when eggs are under the care of adult males. After hatching, mouth‐brooding free‐embryos grew horizontally isometric, except for the snout length that presented quick growth related to the end of endogenous feeding (β₁ = 1.73). Slow growth was observed in head width (β₁ = 0.44) and eye diameter (β₁ = 0.26), taking into account that sensory organs are formed in free‐embryos. The end of the yolk‐sac period was characterized by a direct change from free‐embryo to juvenile, without a true larval period. Juveniles are characterized by growth patterns nearly isometric in all body regions, suggesting that they already bear most of characteristics of adult fish. The quick growth of morphometric variables that are related to sensorial organs before hatching and the increase in horizontal growth after the first 6 weeks (hatched free‐embryos) reflect developmental priorities during the earliest stages where important sensorial organs are being developed for juvenile survival strategies.     

Comparative anatomical study of internal brooding in three anascan bryozoans (Cheilostomata) and its taxonomic and evolutionary implications

The anatomical structure of internal sacs for embryonic incubation was studied using SEM and light microscopy in three cheilostome bryozoans-Nematoflustra flagellata (Waters,1904), Gontarella sp., and Biflustra perfragilis MacGillivray, 1881. In all these species the brood sac is located in the distal half of the maternal (egg-producing) autozooid, being a conspicuous invagination of the body wall. It consists of the main chamber and a passage (neck) to the outside that opens independently of the introvert. There are several groups of muscles attached to the thin walls of the brood sac and possibly expanding it during oviposition and larval release. Polypide recycling begins after oviposition in Gontarella sp., and the new polypide bud is formed by the beginning of incubation. Similarly, polypides in brooding zooids degenerate in N. flagellata and, sometimes, in B. perfragilis. In the evolution of brood chambers in the Cheilostomata, such internal sacs for embryonic incubation are considered a final step, being the result of immersion of the brooding cavity into the maternal zooid and reduction of the protecting fold (ooecium). Possible reasons for this transformation are discussed, and the hypothesis of Santagata and Banta (Santagata and Banta1996) that internal brooding evolved prior to incubation in ovicells is rejected.     

The phylogenetic relationships among non-diplomystid catfishes as inferred from mitochondrial cytochrome b sequences; the search for the ictalurid sister taxon (Otophysi: Siluriformes)

The relationships among families of catfishes are poorly understood and have yet to be the subject of a comprehensive investigation with molecular data. Existing phylogenetic hypotheses are based on morphological data and incompletely resolved. This study analyzed complete sequences of mitochondrial gene cytochrome b for 170 species from 29 of 33 extant families, and focused on the relationships of Ictaluridae to other catfishes. In addition to previous phylogenetic studies, the fossil record, paleogeography, biogeography, and distribution of extant catfish families collectively suggest the location (if extant) of the ictalurid sister taxon to be Northern or Eastern Asia. Of the extant catfishes currently native to this area and included in this analysis, parsimony and Bayesian likelihood analyses recovered Cranoglanis bouderius as the most proximal sister taxon of Ictaluridae. Seemingly, ictalurids and cranoglanidids represent another biogeographic component linking freshwater fishes of North America and eastern Asia, e.g., catostomids and paddlefishes. The results coupled with present-day catfish distributions and inferences from the fossil record collectively suggest the ancestor of Ictaluridae to have invaded freshwaters of North America at the close of the Cretaceous through northeastern Asia and northwestern North America. Other superfamilial nodes supported the results of previous phylogenetic studies of narrower taxonomic scope. Several novel relationships were recovered (including a clade composed of Pimelodidae, Pseudopimelodidae, and Heptapteridae) and these along with sources of systematic error are discussed. A broad sampling of Bagridae permitted an examination of intergeneric relationships within this family and in light of recent morphological and molecular studies.     

Biodiversity of aquatic gastropods in the Mont St-Michel basin (France) in relation to salinity and drying of habitats

Seventy-seven polder and marsh stations were sampled for aquatic and riparian gastropods in the terrestrial basin of Mont St-Michel from March 1994–March 1995 and during a drought in 1996. In addition, four ponds with riparian coppice (bocage) were investigated. Twenty-one stations, mostly in polders, lacked snails; high values of conductivity, and by implication salinity, appeared to make the habitats unfavourable. Only the euryhaline hydrobid Potamopyrgus antipodarum and the amphibious lymnaeid Lymnaea truncatula survived in areas of high conductivity. In associated lagoons, the maximum level of salinity tolerated by freshwater gastropods was 35. Of the 14 species of gastropods collected, Lymnaea peregra and Anisus leucostoma were the most abundant. Stations had 1–7 species and the average gastropod species richness was 3.32 (±1.67). The canals that were the most susceptible to drying had a community of desiccation-resistant species including L. truncatula, Aplexa hypnorum, A. leucostoma and L. peregra. It appears that gastropod assemblages in the terrestrial basin of Mont St-Michel have achieved their current diversity by surviving strong ecological constraints.     

The dynamics of male brooding,mating patterns,and sex roles in pipefishes and seahorses (family Syngnathidae)

Modern theory predicts that relative parental investment of the sexes in their young is a key factor responsible for sexual selection. Seahorses and pipefishes (family Syngnathidae) are extraordinary among fishes in their remarkable adaptations for paternal care and frequent occurrences of sex-role reversals (i.e., female-female competition for mates), offering exceptional opportunities to test predictions of sexual selection theory. During mating, the female transfers eggs into or onto specialized egg-brooding structures that are located on either the male's abdomen or its tail, where they are osmoregulated, aerated, and nourished by specially adapted structures. All syngnathid males exhibit this form of parental care but the brooding structures vary, ranging from the simple ventral gluing areas of some pipefishes to the completely enclosed pouches found in seahorses. We present a molecular phylogeny that indicates that the diversification of pouch types is positively correlated with the major evolutionary radiation of the group, suggesting that this extreme development and diversification of paternal care may have been an important evolutionary innovation of the Syngnathidae. Based on recent studies that show that the complexity of brooding structures reflects the degree of paternal investment in several syngnathid species, we predicted sex-role reversals to be more common among species with more complex brooding structures. In contrast to this prediction, however, both parsimony- and likelihood-based reconstructions of the evolution of sex-role reversal in pipefishes and seahorses suggest multiple shifts in sex roles in the group, independent from the degree of brood pouch development. At the same time, our data demonstrate that sex-role reversal is positively associated with polygamous mating patterns, whereas most nonreversed species mate monogamously, suggesting that selection for polygamy or monogamy in pipefishes and seahorses may strongly influence sex roles in the wild.     

Biparental care in incipient colonies of the dampwood termiteZootermopsis angusticollis Hagen (Isoptera: Termopsidae)

Parental care and division of labor in male and female primary reproductives in incipient colonies of the dampwood termite Zootermopsis angusticolliswere studied by recording repertory sizes, behavior frequencies, time budgets, and transition probabilities of acts. Repertory sizes for males and females were identical, and behaviors were performed at similar frequencies. Time budget data also suggested equal participation in parental care by both sexes. Transition probability analysis suggested that males and females did not organize their behavior in roles. We therefore found no indication of sex-based division of labor during colony foundation and the incipient stages of colony growth. The lack of behavioral specialization may be due to the fact that acts might be related and/or have more than one function, and different tasks are not spatially associated. Our observations are consistent with the hypothesis that monogamous mating systems in termites involve mate assistance.     

Maternal provisioning and possible joint breeding in the burrower bug Adomerus triguttulus (Heteroptera: Cydnidae)

Subsocial burrower bugs (Heteroptera: Cydnidae) provide unique opportunities to investigate evolutionary ecological questions regarding parental provisioning and family dynamics. Observations and marked nutlet‐setting experiments in the field showed that Adomerus triguttulus females progressively delivered mint nutlets into nests harbouring nymphs under the litter. More than one female often attended nymphs, but not eggs, in a nest in the field. The number of nymphs aggregating in a nest with a single female was usually smaller than that in a nest with two females, suggesting the joining of different families and facultative joint parental care. There was a positive correlation between the number of nutlets delivered and the number of nymphs in a nest. The number of attendant females also affected the amount of provisioning; more nutlets were found for second‐instar broods with more females. The effect of brood size on provisioning was confirmed for families under laboratory rearing. Maternal provisioning also varied with the developmental stage of offspring; second‐instar broods received more nutlets than first‐instar broods, with a temporal decrease in provisioning during the moulting of nymphs. Considering the growing evidence of food solicitation signals of young in subsocial insects, the observed finely tuned supply of food by the female could be induced by begging signals from the nymphs.